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Computer Architecture


Princess Sumaya University for Technology Computer Architecture Dr. Esam Al_Qaralleh computer arctecture ~ PSUT * A modern meaning of the term computer architecture ... – PowerPoint PPT presentation

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Title: Computer Architecture

Computer Architecture
Princess Sumaya University for Technology
  • Dr. Esam Al_Qaralleh

  • Review

Course Syllabus
  • Grading
  • The first priority Maximize Learning
  • Your grade will depend on how much you have
  • 2 midterm exams (40 to 50).
  • Quizzes and homework's (20 to 10).
  • Final Exam (40)
  • Activity in the class
  • Questions and discussion in the class give you
    points and improve the quality of teaching.

Course Syllabus
  • Text Book
  • Structured Computer Organization
  • Andrew S. Tanenbaum
  • Prentice-Hall, 4th Edition, 1999
  • Reference Books
  • Computer Architecture A Quantative Approach
  • John L. Hennessy David A. Patterson
  • Morgan Kaufmann, 3ed Edition, 2003
  • Computer System Architecture
  • M. Morris Mano
  • Prentice Hall, 3ed Edition, 1993

Course Syllabus
  • Class Rules
  • Attendance to class should be on time
  • Very late attendance will be count as an absent.
  • Using Mobile Phone is NOT ALLOWED during class.
  • Questions and Discussions is the best way to

What is a digital computer ?
  • A digital computer is a machine composed of the
    following three basic components
  • Input/Output
  • Central Processing Unit (CPU)
  • Memory

The Von Neumann Machine, 1945
  • The Von Neumann model consists of five major
  • input unit
  • output unit
  • ALU
  • memory unit
  • control unit.
  • Sequential Execution

Von Neumann Model
  • A refinement of the Von Neumann model, the system
    bus model has a CPU (ALU and control), memory,
    and an input/output unit.
  • Communication among components is handled by a
    shared pathway called the system bus, which is
    made up of the data bus, the address bus, and the
    control bus. There is also a power bus, and some
    architectures may also have a separate I/O bus.

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  • CPU (central processing unit) is an older term
    for processor and microprocessor, the central
    unit in a computer containing the logic circuitry
    that performs the instructions of a computer's
  • - RISC Reduced Instruction Set Computer
  • -Introduced in the mid 1980s
  • -Requires few transistors
  • -capable of executing only a very limited set
  • instructions
  • - CISC Complex Instruction Set Computer
  • -complex CPUs that had ever-larger sets
    of instructions

RISC or CISC The great Controversy
  • RISC proponents argue that RISC machines are both
    cheaper and faster, and are therefore the
    machines of the future.
  • Skeptics note that by making the hardware
    simpler, RISC architectures put a greater burden
    on the software. They argue that this is not
    worth the trouble because conventional
    microprocessors are becoming increasingly fast
    and cheap anyway.
  • The TRUTH!
  • CISC and RISC implementations are becoming more
    and more alike. Many of today's RISC chips
    support as many instructions as yesterday's CISC
    chips. And today's CISC chips use many techniques
    formerly associated with RISC chips.

Under the hood of a typical CPU
What you need to Know about a CPU
  • Processing speed
  • - The clock Frequency is one measure of how fast
    a computer is ( however, the length of time to
    carry out an operation depends not only on how
    fast the processor cycles, but how many cycles
    are required to perform a given operation.
  • Voltage requirement
  • Transistors (electronic switches) in the CPU
    requires some voltage to trigger them.
  • - In the pre-486DX66 days, everything was 5
  • - As chips got faster and power became a
  • designers dropped the chip voltage down to
    3.3 volts (external Voltage) and 2.9V or 2.5V
    core voltage

More on Voltage Requirements
  • Power consumption equates largely with heat
    generation, which is a primary enemy in achieving
    increased performance. Newer processors are
    larger and faster, and keeping them cool can be a
    major concern.
  • Reducing power usage is a primary objective for
    the designers of notebook computers, since they
    run on batteries with a limited life. (They also
    are more sensitive to heat problems since their
    components are crammed into such a small space).
  • Compensate for by using lower-power semiconductor
    processes, and shrinking the circuit size and die
    size. Newer processors reduce voltage levels even
    more by using what is called a dual voltage, or
    split rail design

More on Dual Voltage Design
  • A split rail processor uses two different
  • The external or I/O voltage is higher, typically
    3.3V for compatibility with the other chips on
    the motherboard.
  • The internal or core voltage is lower usually
    2.5 to 2.9 volts. This design allows these
    lower-voltage CPUs to be used without requiring
    wholesale changes to motherboards, chipsets etc.

Power consumption verses speed of some processors
  • Computers have hierarchies of memories that may
    be classified according to Function, Capacity and
    Response Times.
  • -Function
  • "Reads" transfer information from the memory
    "Writes" transfer information to the memory
  • -Random Access Memory (RAM) performs both
    reads and writes.
  • -Read-Only Memory (ROM) contains
    information stored at the
  • time of manufacture that can only be
  • -Programmable Read-Only Memory (PROM) is ROM
    that can be written once
  • at some point after manufacture.
  • -Capacity
  • bit smallest unit of memory (value of 0 or
  • byte 8 bits
  • In modern computers, the total memory may range
    from say 16 MB in a small personal computer to
    several GB (gigabytes) in large supercomputers.

More on memory
  • Memory Response
  • Memory response is characterized by two
    different measures
  • -Access Time (also termed response time or
    latency) defines how quickly the memory can
    respond to a read or write request.
  • -Memory Cycle Time refers to the minimum period
    between two successive requests of the memory.
  • -Access times vary from about 80 ns ns
    nanosecond 10(-9) seconds for chips in small
    personal computers to about 10 ns or less for the
    fastest chips in caches and buffers. For various
    reasons, the memory cycle time is more than the
    speed of the memory chips (i.e., the length of
    time between successive requests is more than the
    80 ns speed of the chips in a small personal

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  • A Computer transfers data from disk to CPU, from
    CPU to memory, or from memory to the display
    adapter etc.
  • To avoid having a separate circuits between
    every pair of devices, the BUS is used.
  • Definition
  • The Bus is simply a common set of wires that
    connect all the computer devices and chips

Different functions for Different wires of the bus
  • Some of these wires are used to transmit data.
  • Some send housekeeping signals, like the clock
    pulse. Some transmit a number (the "address")
    that identifies a particular device or memory
  • Use of the address
  • The computer chips and devices watch the
    address wires and respond when their identifying
    number (address) is transmitted before they can
    transfer data
  • Problem!
  • Starting with machines that used the 386 CPU,
    CPUs and memory ran faster than other I/O devices
  • Solution
  • - Separate the CPU and memory from all the I/O.
    Today, memory is only added by plugging it into
    special sockets on the main computer board.

Bus Speeds
  • Multiple Buses with different speeds is an option
    or a single bus supporting different speeds is
  • In a modern PC, there may be a half dozen
    different Bus areas.
  • There is certainly a "CPU area" that still
    contains the CPU, memory, and basic control
  • There is a "High Speed I/O Device" area that is
    either a VESA Local Bus (VLB) or an PCI Bus

Some Bus Standards
  • ISA (Industry Standard Architecture) bus
  • In 1987 IBM introduced a new Microchannel (MCA)
  • The other vendors developed an extension of the
    older ISA interface called EISA
  • VESA Local Bus (VLB), which became popular at the
    start of 1993

More Bus Standards
  • The PCI bus was developed by Intel
  • PCI is a 64 bit interface in a 32 bit package
  • The PCI bus runs at 33 MHz and can transfer 32
    bits of data (four bytes) every clock tick.
  • That sounds like a 32-bit bus! However, a clock
    tick at 33 MHz is 30 nanoseconds, and memory only
    has a speed of 70 nanoseconds. When the CPU
    fetches data from RAM, it has to wait at least
    three clock ticks for the data. By transferring
    data every clock tick, the PCI bus can deliver
    the same throughput on a 32 bit interface that
    other parts of the machine deliver through a 64
    bit path.

Things to know about I/O Bus
  • Buses transfer information between parts of a
    computer. Smaller computers have a single bus
    more advanced computers have complex
    interconnection strategies.
  • Things to know about the bus
  • Transaction Unit of communication on bus.
  • Bus Master The module controlling the bus at a
    particular time.
  • Arbitration Protocol Set of signals exchanged
    to decide which of two competing modules will
    control a bus at a particular time.
  • Communication Protocol Algorithm used to
    transfer data on the bus.
  • Asynchronous Protocol Communication algorithm
    that can begin at any time requires overhead to
    notify receivers that transfer is about to begin.

Things to know about the bus continued
  • Synchronous Protocol Communication algorithm
    that can begin only at well-know times defined by
    a global clock.
  • Transfer Time Time for data to be transferred
    over the bus in single transaction.
  • Bandwidth Data transfer capacity of bus
    usually expressed in bits per second (bps).
    Sometimes termed throughput.
  • Bandwidth and Transfer Time measure related
    things, but bandwidth takes into account required
    overheads and is usually a more useful measure of
    the speed of the bus.

  • Both Hardware and Software affect performance
  • Algorithm determines number of source-level
  • Language/Compiler/Architecture determine machine
  • Processor/Memory determine how fast instructions
    are executed

Tasks of Computer Architects
  • Computer architects must design a computer to
    meet functional requirements as well as price,
    power, and performance goals. Often, they also
    have to determine what the functional
    requirements are, which can be a major task.
  • Once a set of functional requirements has been
    established, the architect must try to optimize
    the design.
  • Here are three major application areas and their
    main requirements
  • Desktop computers focus on optimizing
    cost-performance as measured by a single user,
    with little regard for program size or power
  • Server computers focus on availability,
    scalability, and throughput cost-performance,
  • Embedded computers driven by price and often
    power issues, plus code size is important.

Where is the Market?
Applications Change over Time
  • Data-sets memory requirements ? larger
  • Cache memory architecture become more critical
  • Standalone ? networked
  • IO integration system software become more
  • Single task ? multiple tasks
  • Parallel architectures become critical
  • Limited IO requirements ? rich IO requirements
  • 60s tapes punch cards
  • 70s character oriented displays
  • 80s video displays, audio, hard disks
  • 90s 3D graphics networking, high-quality audio
  • 00s real-time video, immersion,

Application Properties toExploit in Computer
  • Locality in memory/IO references
  • Programs work on subset of instructions/data at
    any point in time
  • Both spatial and temporal locality
  • Parallelism
  • Data-level (DLP) same operation on every element
    of a data sequence
  • Instruction-level (ILP) independent instructions
    within sequential program
  • Thread-level (TLP) parallel tasks within one
  • Multi-programming independent programs
  • Pipelining
  • Predictability
  • Control-flow direction, memory references, data

Levels of Machines
  • There are a number of levels in a computer, from
    the user level down to the transistor level.

Computer Architecture
  • A modern meaning of the term computer
    architecture covers three aspects of computer
  • instruction set architecture,
  • computer organization and
  • computer hardware.
  • Instruction Set Architecture - ISA refers to the
    actual programmer-visible machine interface such
    as instruction set, registers, memory
    organization and exception handling. Two main
    approaches RISC and CISC architectures.
  • A computer organization and computer hardware
    are two components of the implementation of a

How Do the Pieces Fit Together?
Instruction Set Architecture
I/O system
Instr. Set Proc.
Memory system
Datapath Control
Digital Design
Circuit Design
Instruction Set Architecture (ISA)
  • Complex Instruction Set (CISC)
  • Single instructions for complex tasks (string
    search, block move, FFT, etc.)
  • Usually have variable length instructions
  • Registers have specialized functions
  • Reduced Instruction Set (RISC)
  • Instructions for simple operations only
  • Usually fixed length instructions
  • Large orthogonal register sets

RISC and CISC Architecture
  • RISC Reduced Instruction Set Computer
  • CISC Complex (and Powerful) Instruction Set
  • What does MIPS stand for?
  • Microprocessor without Interlocked Pipeline
  • MIPS processor is one of the first RISC
    processors. Again, all processors announced after
    1985 have been of RISC architecture.
  • What is the main example of CISC architecture
  • Intel processors (in over 90 computers).

RISC Architecture
  • RISC designers focused on two critical
    performance techniques in computer design
  • the exploitation of instruction-level
    parallelism, first through pipelining and later
    through multiple instruction issue,
  • the use of cache, first in simple forms and later
    using sophisticated organizations and

RISC ISA Characteristics
  • All operations on data apply to data in registers
    and typically change the entire register
  • The only operations that affect memory are load
    and store operations that move data from memory
    to a register or to memory from a register,
  • A small number of memory addressing modes
  • The instruction formats are few in number with
    all instructions typically being one size
  • Large number of registers
  • These simple properties lead to dramatic
    simplifications in the implementation of advanced
    pipelining techniques, which is why RISC
    architecture instruction sets were designed this

Thank You !